This investigation aimed to study the effect of intercropping patterns of onion with fennel and coriander on growth, yield components, chemical constituents and competition indices. Simple experiment based on randomized complete block design with three replications was conducted in Agricultural Research Farm, Faculty of Agriculture, Zagazig University, Egypt during winter seasons of 2013/2014 and 2014/2015. Cropping patterns were allocated to the different planting ratios (onion: fennel or coriander as 1:1, 1:2 and 1:3) and sole onion, sole fennel and sole coriander as a control. Results revealed that alternating one row of each of fennel or coriander with three rows of onion, mostly, gave the highest values of growth parameters, yield per plant and volatile oil production as well as chemical constituents of apiaceous crops in the two seasons. Also, intercropping pattern of 1coriander:2 onion gave the highest values of onion NPK uptake and protein content per bulb. Generally, the highest values of LER (land equivalent ratio), ATER (area time equivalent ratio), LUE (land utilization efficiency) and RCC (relative crowding coefficient) were (1.206 and 1.288), (1.126 and 1.207), (113.81 and 121.99%) and (2.552 and 4.033) in first and second seasons, respectively which were achieved by intercropping pattern of one row of coriander with two rows of onion. Also, aggressivity values indicated that apiaceous component crops (fennel or coriander) were the dominant, whereas onion was the dominated one in intercropping patterns. Generally, these mixtures seem promising in the development of sustainable crop production with a limited use of external inputs. They can be used by the farmers in Sharkia Governorate conditions as they are the most profitable systems with the greatest yield advantages.